Torsional Capacity Research Articles

Torsional Strength of Recycled Coarse Aggregate Reinforced Concrete Beams

This study discusses the torsional capacity of recycled coarse aggregate (RCA) reinforced concrete beams under pure torsion based on the experimental findings available in the literature. The experimental data on RCA specimens were collected and compared with the conventional concrete specimens with key variables, such as compressive strength and longitudinal and transverse reinforcement ratios, as those variables affect the torsional capacity of reinforced concrete beams. Overall, the database consisted of experimental results from 30 RCA specimens and 256 natural coarse aggregate (NCA) specimens. The result shows that specimens with a 100 % replacement ratio have the lowest strength. In addition, as the structural mechanism of torsion is similar to the shear mechanism in reinforced concrete beams, a comparative analysis was performed with RCA specimens subjected to shear force. It was concluded that the RCA has a similar effect in strength reduction for the specimens subjected to torsion or shear with a 100% replacement ratio. However, further study and experimental evidence are required to confirm the applicability of the recycled aggregate to produce and design the structural members.

Effect of Replacement Ratio on Torsional Behaviour of Recycled Aggregate Concrete Beams

In the past two decade, researchers have studied the flexural, shear and bond behaviour of recycled aggregate concrete (RAC) beams. This work intends to analyze the behaviour of RAC beams under pure torsion, despite the lack of information on its behaviour under pure torsion. The coarse recycled concrete aggregates (RCA) extracted from construction and demolition (C & D) waste was used to replace natural coarse aggregates (NCA) in 0 %, 50 %, and 100 % ratio. Their recycling could help preserve the environment and promote sustainability through solid waste management. Six beams, each of size 150 x 250 x 1800 mm were prepared and tested. To detects minor deformation and to achieve the same strength through the out-of-plane direction, 250 mm inbuilt cantilever projections were provided on opposite faces of the beams at a span of 1000 mm along the longitudinal axis. The ultimate torsional capacity of tested beams was lower by 7.41 %, 8.60 % and 13.58 % than ATENA-3D (FEM) for 0 %, 50 % and 100 % RCA. The change in the replacement ratio of aggregate has a low impact on the ultimate torque and angle of twist. Based on the experimental and analytical results, it was established that the torque resistance capacity of the RAC beam was reduced as the % of RCA increased. Similar crack patterns and failure behaviour were observed in RAC and NAC beams in both studies. Therefore, it is practically possible to apply RAC in structural applications under pure torsional loading.

Numerical Analysis of Torsional Reinforcement of Concrete Beams in Unconventional by ANSYS Software

In this study, a finite element analysis is conducted to study the behaviour of RC beams with different configurations of transverse reinforcement under torsion. These configurations of stirrups are traditional closed stirrups, circular spiral stirrups, and inclined rectangular spiral stirrups. The numerical torsional load values are compared with the experimental torsional load values from previous research. The numerical analysis determined by the ANSYS software shows a reasonable agreement with the experimental torsional load values. The numerical results demonstrate that the use of continuous rectangular spiral stirrups improved the torsional response compared to using another type of beam stirrup. Thus, numerical results show that continuous spiral stirrups are effective at increasing torsional capacity. It is also noted that the behaviour of these beams with continuous spiral stirrups is better than the behaviour of the beams with traditional stirrups. The beams with helical reinforcement, which are TB2, TB3, and TB4 spiral reinforcements, greatly enhanced the toughness. The equivalent stresses are 13.709, 13.728, 14.72, and 15.894 MPa, while the equivalent elastic strains are 0.00421, 0.00377, 0.00347, and 0.00539 mm/mm for the beams TB2, TB3, and TB4, respectively. The beam TB4 had the highest stress and strain value, so its strength improved its ductility properties. As a result, the stirrups' configurations enabled the detection of beam failure mechanisms by improving torsional behaviour when compared to the beam's traditional stirrups. As a result, this research adds more knowledge to the literature on the most effective spiral stirrups for transverse reinforcement to improve the torsional behaviour of beams. Doi: 10.28991/CEJ-2023-09-01-04 Full Text: PDF

Meso‐scale modeling of size effect on pure torsional failure of concrete‐filled steel tubular columns

AbstractThe mechanical properties of concrete‐filled steel tubular (CFST) columns with different sizes under torsional load were studied, aiming to further explore the pure torsional failure mechanism and size effect behavior of CFST columns. First, a 3D meso‐scale numerical model of CFST is established and compared with the existing experimental data. Second, the torsional failure mechanism of CFST column under different section sizes, constraints (confinement coefficient), and cross‐sectional shapes is considered. Results show that: (1) the nominal torsional strength of CFST columns presents a size effect, and the columns with square cross‐section present stronger size effect than the ones with circular shape; (2) with the increase of the confinement coefficient, the size effect of the nominal torsion strength is weakened. Finally, considering the quantitative influence of the size effect, a formula for calculating the pure torsional capacity of CFST columns was developed.

Torsional Behavior of RC Beams with Transverse Openings Strengthened by Near Surface Mounted-Steel Wire Rope Subjected to Repeated Loading

The presence of the openings negatively effects on the strength of the beams where they act as a weak point because of the sudden change in the cross-section of the beam, so it becomes necessary to make strengthening for the beams to resist the effect of the openings and improve the strength of the beams, especially if the beams are subjected to repeated loads because of its effect on the strength at the failure. This paper studies the effect of the openings on the beams subjected to repeated loading and determine the extent of the increase in the strength of the beams when strengthened by the NSM technique. The experimental program included casting and testing fifteen RC beams, six of them considered as a control beams (three with strengthening and three without strengthening), and nine of them having circular transverse openings in different locations and strengthened by the NSM technique. Every type of beams is tested under three different types of loads (monotonic, constant repeated load, and incremental repeated load). All of the beams have the same dimensions and same reinforcement. The results show that all the beams with transverse openings are affected by repeated loads where the ultimate torque decreases and the twist angle increases. The existence of openings has a noted effect on reducing the ultimate torque, whereas the percentage of decrease in the ultimate torsional capacity reached 43.83% at the beam where the opening location is closest to the support (at the quarter of the clear span) and subjected to constant repeated loads, and the ultimate torque is significantly improved when the opening position is moved away from the supports. Also, the existence of strengthening reduced or eliminated the influence of openings on the ultimate torque compared with related non- strengthened beams.

Determination of Ultimate Torque and Twist of High Strength RC Beams with Ferrocement “U” Wraps: Different Approaches

Designers are more interested in strength at cracking rather than ultimate strength. Still then beyond cracking, the structures are able to sustain more loads. So, determination of ultimate strength is an important parameter in design field. Evaluation of ultimate torsional capacity of high strength distressed beams with ferrocement “U” wrap has been presented here. The evaluation procedure involves experimental results, results obtained by analytical method. As the above two methods are not providing quick solution, rather than the first one is based on destruction of prototype structure for evaluation of strength. Other methods such as soft computing methods have been employed. Two methods MARS and WASPAS are employed here to compute the torsional strength of “U” wrapped beams. These two methods provide quick solutions to estimate the torque and twist at ultimate stage. Predicted values by these methods are within acceptable limits. At ultimate stage , the “U” wrapped beams are able to resist torque more than 41.37% than the unwrapped beams and a completely over reinforced beam resists 98.01% more than plain “U” wrapped beams. Under reinforced “U” wrap beams have undergone 23.9 times more twist than that of plain “U” wrap beams. This proves effectiveness of “U” wrap on periphery of distressed beams.

A Parametric Study on Behavior of Elliptical Cantilever Deep Beams

This parametric study used finite element method (ETABS 2019), on 20 elliptical reinforced concrete cantilever deep beam specimens that have rectangular sections. Five parameters were taken into consideration: beam height, beam width, concrete compressive strength, load position and load type. Results showed that when the beam height was increased by 12%–66.5%, the negative and torsional moments and load capacity increased by about 11.23%–76.33%, 11.2%–77% and 11.1%–78%, respectively, whereas deflection decreased by about 15%–39%. The negative and torsional moments and load capacity increased by 26.13%–166.53%, 27%–172.5% and 28%–180%, respectively, and a decrease in deflection of about 1.73%–2.3% took place when beam width increased by about 14.3%–81%. In addition, increasing the compressive strength of concrete by 7.5%–36% led to an increase in the negative moments, torsional moments, load capacity, and deflection by about 8.22%–19.2%, 8.7%–20.4%, 9.4%–22% and 4.7%–7.1%, respectively. When changing the load type from concentrated to uniformly distributed over a third of the span’s length, two-thirds of the span’s length and then over the full span’s length, the negative moments increased by 5.23%, 8.47% and 52.67%, whereas torsional moments decreased by 1.1%, 1.12% and 16%, respectively. Finally, placing the concentrated load at a distance of 0.75, 0.5 and 0.25 of the span lengths led the negative moments to increase by 56.9%, 102.3% and 110%, respectively, whereas torsional moments decreased by 8.64%, 25%, and 58.3%, respectively. The load capacity increased by 87.5%, 243.75% and 556.25%, respectively, accompanied by a decrease in the deflection of the free end by 3.24%, 17.65% and 49.8%, respectively.

Torsional behavior of GFRP-reinforced concrete pontoon decks with and without an edge cutout

Using glass fiber-reinforced polymer (GFRP) bars in precast concrete pontoon decks in aggressive marine environments would eliminate corrosion problems encountered with steel reinforcement. Although wave action usually subjects pontoon decks to torsion, but little is known about the behavior of such structures. Moreover, nothing is known about the effects of cutouts on the torsional behavior of pontoon decks. This study experimentally investigated the torsional behavior of GFRP-reinforced concrete (RC) pontoon decks in terms of the effect of edge cutouts, reinforcement-bar distribution, and rotation direction. The results show that the bar configuration affected the failure behavior and torsional capacity of the GFRP-reinforced concrete decks under torsion. The decks with double-layer reinforcement exhibited slower and narrower cracking growth in the post-cracking stage than the decks with single-layer reinforcement. In addition, the edge cutouts reduced the cracking torque of the solid rectangular decks by an average 17%. The torsional behavior of the GFRP-reinforced planks can be accurately described by the ACI318-14 equation in the cracking stage, while the decks’ post-cracking torsional rigidity can be predicted accurately from the contribution of the GFRP bars.

Development of Prediction Models for the Torsion Capacity of Reinforced Concrete Beams Using M5P and Nonlinear Regression Models

Torsional strength is related with one of the most critical failure types for the design and assessment of reinforced concrete (RC) members due to the complexity of the associated stress state and low ductility. Previous studies have shown that reliable methods to predict the torsional strength of RC beams are still needed, namely for over-reinforced and high-strength RC beams. This research aims to offer a novel set of models to predict the torsional strength of RC beams with a wide range of design attributes and geometries by using advanced M5P tree and nonlinear regression models. For this, a broad database with 202 experimental tests is used to generate highly reliable and resilient models. To build the models, three independent variables related with the properties of the RC beams are considered: concrete cross-section area (area enclosed within the outer perimeter of the cross-section), concrete compressive strength, and torsional reinforcement factor (which accounts for the type—longitudinal or transverse—amount, and yielding strength of the torsional reinforcement). In contrast to multiple nonlinear regression approaches, the findings show that the M5P tree approach has the best estimation in terms of both accuracy and safety. Furthermore, M5P model predictions are far more accurate and safer than the most prevalent design equations. Finally, sensitivity and parametric studies are used to confirm the robustness of the presented models.

Behavior of 3D-printed polymers under monotonic torsion – A database of 15 different materials

A comprehensive study was carried out to assess the performance of various 3D-printed polymers under monotonic torsion. To the best knowledge of the authors, studies on the torsional behavior of 3D-printed polymers are limited. Fifteen different materials were 3D-printed using the fused deposition modeling (FDM) approach in a flat orientation. For each series, two raster angles i.e., ± 45° and 0°/90° degrees were considered. Circular specimens with a diameter of 10 mm were subjected to a torsional moment with a rate of 0.2 mm/min. Results showed superior performance of specimens with a raster angle of ± 45° in comparison to their 0°/ 90° counterparts. Besides, shear moduli and linear energy absorption per unit volume of the specimens were compared and discussed. Specimen PAHT-CF (polyamide high temperature; CF: carbon fiber) (average shear stress: 49.3 MPa) had the overall best performance in all the investigated parameters; failure of specimens except for polypropylene (PPJET), and thermoplastic polyurethane (TPU) was brittle and sudden and initiated between layers rather than inside layers (i.e., filament fracture); incorporation of carbon fiber didn’t necessarily contribute to improved torsional capacity or ductility. Finally, idealized multi-linear curves were proposed which can aid in the numerical simulation of various 3D-printed polymers. • The performance of 15 different 3D-printed polymers was studied under monotonic torsion. • Idealized multi-linear shear stress-shear strain curves were proposed for numerical simulations.

Torsional behaviour of tapered concrete-filled double-skin steel tubular columns with large hollow ratios

Tapered concrete-filled double-skin steel tubular columns with large hollow ratios (LHR-CFDSTs) possess light self-weight and good lateral rigidity. They exhibit tremendous potential in lateral load-critical structures, including large-span buildings, wind turbine towers and offshore infrastructures. In these structures, in addition to axial force and bending moment, columns are also commonly subjected to considerable torque. Although the compressive/flexural behaviour of tapered LHR-CFDST columns has attracted attention from researchers, studies on the torsional performance and mechanism are limited. This paper thus presents a comprehensive analytical study on the torsional behaviour of tapered LHR-CFDST columns on the basis of previous experimental research. Numerical analyses were conducted to investigate the influence of the key parameters. Full-range torsional characteristics of the column were revealed with regard to the typical torque–torsional angle relation, the stress development of the concrete and the contact between components. Load distributions as well as the effective twist length were discussed to understand the mechanism of the column under torsion. It is found that significant torsional deformation, oblique concrete cracks and struts, the compressive stress of concrete and the contact pressure all develop concentratedly within the effective twist length, which reflects the segments of the tapered column with a relatively weak torsion-resistant ability. Lastly, a torsional capacity prediction method was proposed by refining the previous theoretical model and it exhibits favourable accuracy for tapered LHR-CFDST columns with tapered angles higher than 1.50°.

The Behavior of Hybrid Fiber RC Shear Walls Subjected to Monolithic Pure Torsion: An Analytical Study

The reinforced concrete (RC) shear walls are widely used to serve as the primary lateral load-resisting member in the high-rise buildings. An experimental investigation and analysis of the mechanical behaviour of hybrid fiber reinforced self-compacting concrete (HFRSCC) shear walls under pure torsion moment is presented in this paper. The nine HFSCC shear walls with the same height and longitudinal reinforcement ratio analytically were tested under pure torsion moment and no axial load. The effect of hybrid fiber ratio and horizontal reinforcement amount and aspect ratio on the failure characteristics, torsional behaviour, energy dissipation capacity of squat shear walls was studied. Result indicate that both hybrid and horizontal reinforcement ratio are increased the maximum torsional moment capacity and twist angle and that the hybrid fiber ratio is the key parameter that determines the failure mode of the HFSCC shear walls.

Performance of strengthened RC beams with torsional CFRP wraps in monolithic framed structures: Experimental and numerical investigation

The performance of externally applied wraps to simply supported reinforced concrete (RC) beams under pure torsion has been well-defined in the literature. In most cases, the previous research works utilised carbon fibre reinforced polymers (CFRP) wraps with different configurations to enhance the beams torsional capacities. While the effectiveness of these wraps in monolithic framed beams in RC buildings is less understood. Further, there is still a lack of information regarding the influence of interacted-combined loads on both the wrapped beams and the joined columns. This paper deals with the presence of different wrapping schemes on the response of framed beams that joined to columns, and how different levels of eccentric torsional forces combined with bending and shear forces can alter the damage state. The experimental programme of this study involved a series of beam-column assemblies tested under concentric and eccentric combined loads. Based on the test observations, a nonlinear finite element (FE) procedure is proposed and validated for simulating the full response of RC beam-column assemblies. This validated FE procedure is then used to explore critical parameters which govern the wraps performance and the failure modes. The outcomes of this study provide comprehensive insights into the role of the interacted forces and the wrapping configurations on the developed deformations and the members integrity. In particular, the results confirmed that the torsional force adversely affected the flexural capacities in proportion to the ratio of the torsion applied. Meanwhile, the interacted forces can induce substantial strain and damage levels that can be extended to the joined column. The contribution of CFRP wraps is found to be limited to the concrete strut’s capacity and the extent of torsional shear-flow in consistent with the imposed loads ratios and the developed truss mechanism.

The Pure Torsional Behavior of Hiybrid Fiber RC Shear Walls

The reinforced concrete (RC) shear walls are widely used to serve as the primary lateral load-resisting member in the high-rise buildings. An experimental investigation of the mechanical behaviour of hybrid fibre (carbon and steel) reinforced self-compacting concrete (HFRSCC) shear walls under pure torsion moment is presented in this paper. The nine HFRSCC shear walls with the same longitudinal reinforcement ratio were tested under pure torsion moment and no axial load. The effect of hybrid fibre ratio and horizontal reinforcement amount and aspect ratio on the failure characteristics, torsional behaviour, energy dissipation capacity, ductility of shear walls was studied. Results indicate that both hybrid and horizontal reinforcement ratio are increased the ultimate torsional moment capacity and angle of rotation and that the hybrid fibre ratio is the key parameter that determines the failure mode of the HFRSCC shear walls. Torsional moment capacity increased, when the hybrid fiber ratio rose up from 0% to 1.0% and then 1.5%. However, this increase was larger in case of increasing the hybrid fiber ratio from 0% to 1.0%. Increasing the hybrid fiber ratio from 1.0% to 1.5% did not result in a performance increase as in the first case.

Enhanced Torsion Mechanism of Small-Scale Reinforced Concrete Beams with Spiral Transverse Reinforcement

The nonlinear torsional behaviour of small-scale reinforced concrete (RC) beams with continuous staggered spiral as transverse reinforcement stirrups is experimentally investigated. Twelve miniatures RC beams were tested under torsion load considering the closed shape of stirrups and compared with continuous staggered spiral ones. All miniatures beams were scaled down to be one-eighth the prototype beam size. The main parameters considered in this research are stirrup spacing and its configurations. Small scale RC beams were taken into account in the existing study because of their construction simplicity and financial feasibility. Mortar without coarse aggregate was applied instead of concrete to reduce the size effect of applying small scale models. Ongoing research trials have been carried out to obtain an efficacious approach to boost torsion failure mechanisms because brittle torsion failure of RC structural elements should be avoided. This study emphasized boosted torsion capacity, dissipated energy, and helical crack propagation. During testing, the primary cracking torsion moment, ultimate torsion moment, peak twist angle, and failure mechanism of the beams were inspected. The use of spiral stirrups showed great enhancement of the torsional behaviour of samples. It was observed that using spiral stirrups rather than closed stirrups could result in a substantial increase in torsion capacity and dissipated energy of 87.7% and 89.8%, respectively. As a result, the predicted capacities of the RC beams prototype were estimated in detail, taking account the scale down factor implemented by the authors. Values obtained based on international specifications and guidelines were used to compare the experimental results. Doi: 10.28991/CEJ-2022-08-11-019 Full Text: PDF

Effect of type, amount and configuration of reinforcement in HSC box-girders reinforced with BFRP bars and steel stirrups under torsion-shear-bending

There has been no research on the performance of high-strength concrete (HSC) hollow members reinforced with basalt fiber reinforced polymer (BFRP) bars and steel stirrups under combined torsion (T), shear (V), and moment (M); this study examines the above scenario. Six specimens of identical size and length were constructed and tested, each having a total quantity of reinforcement of 2.5%. The supports were restrained against twisting and the load was applied at a transverse eccentricity of 1.67 m at midspan, producing the required T-V-M ratio, with torsion as the dominant action. The proportion of longitudinal to transverse reinforcement, the number and diameter of longitudinal BFRP bars, and the diameter and spacing of steel stirrups, were the factors investigated. The experimental results were evaluated in terms of strength and stiffness, deflection and angle of twist, cracking pattern, and failure modes. For the same total amount of reinforcement, the best results were achieved utilizing specimens with BFRP bars and steel stirrups of smaller diameter at closer spacings. Employing more longitudinal BFRP bars ( ρ l = 1.58 ρ t ) produced better outcomes than using more steel stirrups ( ρ t = 1.32 ρ l ), indicating that the amount of BFRP bars is as critical as or more important than the amount of steel stirrups. The experimental results of cracking torque and twist, and ultimate torque were compared to the code and other available expressions. It was found that ACI, CSA, and EC equations can be extrapolated without any modification to predict the torsional strength of HSC box-girders longitudinally reinforced with BFRP bars under combined T-V-M. In addition, a new approach was suggested, which can predict the ultimate torsional twist capacity reasonably well.

Influence of torsional stiffness in double-angle open-web joist and joist girder chords

The double angle chords of open-web steel joists are often designed to efficiently support loading with relatively slender sections, which introduces buckling instabilities that are treated differently by various design standards. This study investigates the buckling behavior of double angles, focusing on the importance of flexural–torsional buckling. A theoretical inelastic buckling investigation considering current design practices and known steel behavior demonstrates how flexural–torsional buckling does not control for all double angle configurations. Subsequent investigation focuses on double angles theoretically susceptible to flexural–torsional buckling, while implementing finite element modeling of full joist structures and isolated chord segments. The resulting elastic eigenbuckling analysis and geometrically and materially nonlinear analysis with imperfections captures significant twisting of individual angles in the built-up section; however, global flexural–torsional buckling was not observed to control. Most double angle configurations are controlled by flexural buckling due to an increased flexural–torsional buckling capacity. This result is attributed to the observed increased torsional stiffness of the chords, which is typically not considered in design. A supplementary investigation indicated this torsional stiffness was primarily a result of torsion being transferred through the stiff chord-to-chord connections, which do not exist in all double angle members. Accounting for the additional torsional stiffness in a theoretical inelastic buckling calculation leads to flexural–torsional buckling not controlling the design of most double angle cross sections considered in this study. Overall, this study indicates that designing double angles in joist structures by only considering flexural buckling with local buckling is reasonable with current industry practices.

Torsional Improvement of RC Beams Using Various Strengthening Systems

Many structural elements are subjected to a significant torsional moment that affects the structural design and may require strengthening. This paper presents different effective strengthening techniques to enhance the torsional capacity of reinforced concrete (RC) beams. An experimental and numerical investigation was undertaken to evaluate the efficacy of utilizing various strengthening systems. The experimental program included six full-scale RC beams with a cross-section dimension of (150 mm × 300 mm) and a length of 1500 mm, split into one beam without strengthening as a control beam, and six beams strengthened with various materials. The various strengthening materials were wrapped aluminum strips with anchorage bolts, wrapped stainless steel strips with anchorage bolts, wrapped glass fiber reinforcement polymer (GFRP), one layer of wrapped steel wire, and two layers of wrapped steel wire meshes along the beam. The results showed that the ultimate torque of the beam strengthened by wrapped aluminum strips and the beam strengthened by wrapped stainless steel strips was larger than the control beam by about 32% and 40%, respectively, because the strips acted as an external reinforcement. In addition to the strengthening systems, using aluminum strips and stainless steel strips is effective in raising the capacity to a similar degree despite the high cost of the stainless steel strips. The ultimate torque of the beams strengthened by GFRP, one-layered wrapped steel wire meshes, and two-layered wrapped steel wire meshes along the beam is larger than the control beam by about 62%, 118%, and 163%, respectively, in addition to the ultimate angle of twist, which was larger than the control beam by about 53%, 93%, and 126%, respectively. This showed that the strengthening using the two-layered wrapped steel wire meshes along the beam would be very significant in increasing the ultimate torque strength. Moreover, the strengthened beam by two-layered fully wrapped steel wire meshes along the beam developed the highest ductility factor compared to all strengthened beams; in contrast, the beam strengthened by GFRP had less ductility. To verify the outcomes of the experimental tests, a finite-element program, ABAQUS, was performed. Finally, an excellent agreement between the experimental and numerical results was obtained.

Torsional capacity evaluation of RC beams using an improved bird swarm algorithm optimised 2D convolutional neural network

This study presents the application of deep learning technology in torsional capacity evaluation of reinforced concrete (RC) beams. A data-driven model based on 2D convolutional neural network (CNN) is established, where model inputs contain the beam width, beam height, stirrup width, stirrup height, concrete compressive strength, steel ratio of longitudinal reinforcement, yield strength of longitudinal reinforcement, steel ratio of transverse reinforcement, yield strength of transverse reinforcement and stirrup spacing. To enhance the prediction accuracy of the proposed model, an improved bird swarm algorithm (IBSA) is leveraged to optimise the hyperparameters of CNN in the training phase. A comprehensive dataset, comprising 268 groups of laboratory tests of RC beams collected from published articles, is used for model development and validation. The results show that the proposed 2D CNN with hyperparameter optimisation exhibits high performance in predicting torsional strength of RC beams, which outperforms other machine learning models, building codes and empirical formula in terms of a series of evaluation metrics.

The Role of Fiber-Type Reinforcement in the Torsional Behavior of Solid and Hollow Reinforced Concrete Beams

In order to improve the strength of concrete structures, the fiber reinforcement of concrete has become an essential factor. This study was conducted as an experimental program to gain a better understanding of how the variance of fiber shape and type affect the structural performance of solid and hollow reinforced concrete beams using four types of fiber (hooked-end, straight, corrugated steel fiber, and polyolefin fiber) under torsion. For this purpose, ten fiber-reinforced concrete beam specimens, five solid and five hollow, with square cross sections were fabricated using the adopted types of fiber. The role of fiber type in the improvement of the mechanical properties of hardened concrete was also investigated. The results revealed that the mechanical properties of the hardened concrete mix was enhanced by using the existing fiber in concrete, and the higher improvement was shown in the splitting tensile strength test and modulus of rapture in specimens with corrugated steel fiber. The torsional behavior of solid and hollow beams was improved significantly, and the capacity of torsional strength was especially improved for the beams strengthened with corrugated steel fiber. Straight and polyolefin fiber showed a slight improvement in the concrete mechanical properties and less enhancement in the torsional capacity of the tested beams. However, the tested beams reinforced by polyolefin fiber provide better ductility under torsion compared with the use of other types of fiber.